1. Field
The present invention relates to a method and device for the determination of position.
2. Brief Description of Related Developments
The integration of different positioning methods into portable terminal devices has made it possible for a user of such a terminal to determine his/her geographical position. The use of satellites for the determination of position has given rise to the global GPS navigation system (Global Positioning System). The evolution of mobile communication systems and mobile terminals has also given rise to other types of positioning method, for example the E-OTD (Enhanced Observed Timing Difference) system, which is based on the measurement of differences in reception times of signals sent by several base stations at a mobile terminal.
In the development of methods and devices for the determination of position, emphasis has so far been placed mainly on the interaction between one application used in the device and one positioning method. An example of this kind of device is a portable GPS navigation device, which enables a user of the device to determine his/her position using the Global Positioning System and to display positioning information including, for example longitude and latitude information, on a display of the device. Since the reliability of different positioning methods under different geographical conditions varies, the problems that this may cause to the user of the device have been solved by enabling more than one positioning method to be used in a single terminal. In this way, the most suitable positioning method for any given situation can be used e.g. by selecting the method to be used from more than one available alternative. For example, the GPS positioning system is particularly well suited for use when travelling by road in a vehicle. In locations where the reliability of the GPS system is not the best possible, such as inside buildings, other positioning methods that function better can be used, for instance the E-OTD or TOA (Time to Arrival) methods.
A method and a device of this kind are presented in patent publication GB 2 322 248 A, in which the terminal comprises a single positioning application, capable of using several different positioning systems and changing the positioning method automatically if the positioning method in question becomes inoperative. In GB 2 322 248, the application using the positioning data provided by the various positioning methods, only provides the user with information that relates to the determination of position. In other words, the application only makes limited use of the positioning data. In the future, however, as applications further develop and diversify, different applications in mobile terminals will utilise positioning information to an increasing extent and in more complex and varied ways, not limited to the straightforward presentation of positioning-related information, to the user of the device. It is likely that a single terminal will comprise several applications and services utilising positioning information as well as several available positioning methods. For example, it is likely that future mobile terminals, for example, those developed in connection with 3rd generation mobile communication networks, will provide far more varied positioning-based applications than currently available. These applications may include, for example, navigation systems incorporating map-based displays for tracking the user's position, or applications designed to locate a particular type of service or retail outlet closest to the user's current location.
As the number of applications in a mobile terminal that require access to positioning data increases and the number of different positioning methods to which an application may have access also increases, a need will arise to manage and control the use of the positioning methods by the applications in an efficient manner. The need for efficient control of the positioning methods by the applications will become even more important as the complexity of the positioning-related tasks performed by the applications increases.